There is a way to figure it out if they give the odds for getting the SPs and also the odds of getting a serial numbered card. Then it just becomes a quick math equation to figure it out.
For example:
If odds of getting an SP are 1:10, and there are 50 different SP cards in the set,
and odds of getting a card serial numbered to 25 are 1:250, and there are 100 cards in that set,
then the math would be
X*50/(1/10) = 25*100/(1/250)
Where X is the quantity of each of the 50 SP cards. Now solving for X, yields the following result:
X = 1250